1. Technical Field
The present invention relates in general to a method and system for securing networks. Still more particularly, the present invention relates to an improved system and method for providing multiple authentication schemes to authenticate computer systems that are members of a virtual private network.
2. Description of the Related Art
In today's modern environment, many businesses and organizations deal with global markets and have global logistic concerns. Many organizations have facilities disbursed across the country or even around the world. Despite their global presence, these organizations need a way to maintain fast, secure and reliable communications with individuals and other offices throughout the world.
Until recently, fast, secure and reliable communication has meant the use of leased lines to maintain a Wide Area Network (WAN). Leased lines, ranging from ISDN (Integrated Services Digital Network, 144 Kbps) to OC3 (Optical Carrier-3, 155 Mbps) fiber, provided a company with a way to expand their private network beyond their immediate geographic area. A WAN had obvious advantages over a public network like the Internet when it came to reliability, performance and security. But maintaining a WAN, particularly when using leased lines, can become quite expensive and often rises in cost as the distance between the offices increases. In addition, using WANs is not a scalable solution as the number of interconnections rises exponentially as new locations are added.
In essence, a Virtual Private Network, or “VPN,” is a private network that uses a public network (usually the Internet) to connect remote sites or users together. To make communication between computers private, VPNs use security methods, such as encryption, to maintain privacy. Instead of using a dedicated, real-world connection such as leased line, a VPN uses “virtual” connections routed through the Internet from the company's private network to the remote site or employee.
A well-designed VPN can greatly benefit a company. For example, it can: extend geographic connectivity, improve security, reduce operational costs versus traditional WAN, reduce transit time and transportation costs for remote users, improve productivity, simplify network topology, provide global networking opportunities, provide telecommuter support, provide broadband networking compatibility, and provide faster ROI (Return On Investment) than traditional WAN. A well-designed VPN, therefore, should incorporate features for security, reliability, scalability, network management, and policy management.
In a VPN, each remote member of the network is able to communicate in a secure and reliable manner using the Internet as the medium to connect to a private local area network, or “LAN.” A VPN can grow to accommodate more users and different locations much easier than a leased line. In fact, scalability is a major advantage that VPNs have over typical leased lines. Unlike leased lines, where the cost increases in proportion to the distances involved, the geographic locations of each office matter little in the creation of a VPN.
A well-designed VPN uses several methods for keeping connections and data secure. Firewalls provide a strong barrier between private networks and the Internet. Firewalls can restrict the number of open ports, what type of packets are passed through, and which protocols are allowed through. Encryption is used to encode all the data that one computer is sending to another into a form that only the other computer will be able to decode. Two modes of authentication are used on VPNs: pre-shared keys and digital signatures.
Pre-shared key encryption means that each partner in a VPN has a secret “key” that it can use to authenticate the remote identifier of a VPN. Pre-shared key encryption requires that you know which computers will talk to each other, and that you install the same key on each one.
Digital signature authentication, on the other hand, uses a combination of a private key and a public key. The private key is known only to your computer while the public key is given by your computer to any computer that wants to communicate securely with it. To decode an encrypted message, the receiving computer must use the public key provided by the originating computer. Public keys are bound to an identity, such as a business or a user, by using “digital certificates” that are typically issued by a trusted third party.
The key is based on a hash value. This is a value that is computed from a base input number using a hashing algorithm. The important thing about a hash value is that it is nearly impossible to derive the original input number without knowing the data used to create the hash value. Public keys generally use complex algorithms and very large hash values for encrypting.
On a typical VPN, the authentication of the initial connection is accomplished using public key algorithm. Once the connection is established and authenticated, keying material is sent from one computer to the other and the connection switches to symmetric encryption, such as DES or Triple DES. Symmetric encryption is used during data transfer because the amount of time decoding data is reduced.
The Internet Protocol Security Protocol (IPsec) provides enhanced security features such as strong encryption algorithms and comprehensive authentication. IPsec has two encryption modes: tunnel and transport. Tunnel mode tunnels the original packet and builds a new IP header, while transport mode inserts the IPsec payload between the IP header and the data. Systems that are IPsec compliant can take advantage of this protocol. Also, all devices negotiate security parameters, but they must have compatible security policies set up. IPsec works well on both Remote-Access and Site-to-Site VPNs. IPsec must be supported at both tunnel interfaces to work.
Many VPNs rely on tunneling to create a private network that reaches across the Internet. Essentially, tunneling is the process of placing an entire packet within another packet and sending it over a network. The protocol of the outer packet is understood by the network and both points, called tunnel interfaces, where the packet enters and exits the VPN. Tunneling uses three different protocols: (1) carrier protocol: the protocol used by the network that the information is traveling over; (2) encapsulating protocol: the protocol that is wrapped around the original data; and (3) passenger protocol: the original data (IPX, NetBeui, IP) being carried.
Tunneling has important implications for VPNs. For example, a packet that uses a protocol not supported on the Internet (such as NetBeui) can be placed inside an IP packet and sent it safely over the Internet. Or a packet that uses a private (non-routable) IP address can be placed inside a packet that uses a globally unique IP address in order to extend a private network over the Internet. Tunneling is also necessary for gateways because the IP header needs to have the gateway IP address in it.
An analogy of tunneling is having a computer delivered to you by a courier service. The vendor packs the computer (passenger protocol) into a box (encapsulating protocol) which is then put on a courier truck (carrier protocol) at the vendor's warehouse (entry tunnel interface). The truck (carrier protocol) travels over the highways (Internet) to your home (exit tunnel interface) and delivers the computer. You open the box (encapsulating protocol) and remove the computer (passenger protocol).
A challenge with VPNs, however, is that there are many configuration options. VPNs may use different authentication (security) schemes with different certificate authorities and different Certificate Revocation List (CRL) servers. In addition, the CRL information may be retrieved from a variety of network locations using a variety of protocols.
What is needed, therefore, is a way to dynamically determine a location and protocol to use when retrieving CRL information to improve security and performance.